1. Field of the Invention
This invention pertains to a method and an apparatus for taking x-rays and more particularly to a method and an apparatus for providing a reproducible set of x-rays of a patient in a prone position.
2. Description of the Related Art
A set of x-rays is taken before orthognathic surgery, which is surgery to reposition the bones of the face and jaw. A surgical treatment objective is developed and traced onto x-ray films to provide a plan for movement of hard tissues in and around a person's jaw. A second set of x-rays is taken after the surgery, but typically a couple of days after the surgery, when the patient is able to stand or sit for orthodontic x-rays. The post-surgery x-rays are compared to the surgical treatment objective to determine whether the desired results were achieved. If the desired results were not achieved, then the patient must be operated on a second time, leading to the additional risk, discomfort and expense of a second surgical procedure. Even a very small deviation between a desired result and an actual result can be unacceptable because misalignment of a person's jawbone can result in poor cosmetic and functional result and temporomandibular joint pain.
The need for orthognathic surgery typically arises as a procedure for correcting an improper location of jawbones or teeth. Victims of trauma to the face, such as victims of car accidents and gun shot wounds, also have a need for pre-surgery and post-surgery x-rays of the jawbones and teeth. Trauma victims and other persons, such as invalids, are frequently unable to stand or sit while a set of orthodontic x-rays are taken. It is thus necessary to take the x-ray while the person is in a prone position, such as on an operating table. However, x-rays currently taken of a patient in a prone position differ in magnification and orientation from one set of images to a second set of images taken subsequent in time.
In U.S. Pat. Nos. 4,566,444; 4,579,117; and 4,683,582, issued to Spolyar, a portable cephalostat is disclosed as having a frame-like base sub-assembly that provides an area upon which a patient's head can rest. The base sub-assembly provides a support for supporting locating arms that serve to locate the patient's head in a selected position. An x-ray film is secured to the base sub-assembly in various positions, one below the patient's head and others on each side of the head generally parallel to a mid-sagittal plane of the patient's head. Spolyar provides a telescoping rod, resembling an antennae, as an indicator of a desired location for an anode of an x-ray machine. Spolyar also discloses calculations for determining a degree of magnification on an x-ray film, which is related to distances between the film and the patient and the patient and the anode of the x-ray machine. There is no rigid capture of the patient's head relative to an x-ray source. X-ray films taken subsequent in time are not sufficiently identical to x-rays taken earlier in time. The level of precision is inadequate.
U.S. Pat. No. 5,148,454, issued to Coffman, discloses an apparatus for conducting cranial x-ray tomography and radiography. An apparatus is disclosed having a horizontally oriented, motor driven rotatable shaft for imparting controlled rotation to an elongate support member having an x-ray source and a film holder provided at an opposite end. The apparatus includes a cephalometer that supports a patient's head at a fixed position during x-ray tomography and radiography procedures. However, the apparatus is not portable and is not suitable for taking x-rays of a patient in a prone position.
U.S. Pat. No. 4,831,645, issued to Guenther et al., discloses an apparatus for positioning the head of a patient for producing dental panorama tomograms. The apparatus has an arrangement for positioning the head in a desired position relative to a fixed point with respect to at least one projection plane. This point in turn assumes a definite position relative to a central ray extending from an x-ray tube towards an x-ray picture. A silhouette of the head is produced and projected, and an actual position is compared to a desired position. The head is moved until the silhouette of the actual position is congruent with the silhouette of the desired position, which brings the head into the desired position for x-ray exposure.
U.S. Pat. No. 4,759,361, issued to Gallop et al., discloses a telescoping adjustment assembly for a head positioner used in a cephalostat. A cephalostat housing has a pair of ear posts carried outwardly of the cephalostat housing and moveable toward the cephalostat housing so that the mid-sagittal of the head may be repetitively positioned in a same alignment to obtain a consistent series of radiographs over time. A patient's dentition and temporomandibular joint can be located in virtually the same arrangement relative to the film for x-rays taken at different times, such as for determining a patient's progress during orthodontia. However, the apparatus has a wall plate support for attachment to a wall and is thus not portable or suitable for use in an operating room.
U.S. Pat. No. 4,783,793, issued to Virtia et al., discloses a panoramic tomography x-ray apparatus such as for obtaining images of dental systems. An x-ray tube of an x-ray generator and an x-ray film cartridge are mounted to an arm that is rotatable. A control system for controlling the functioning of the equipment and apparatus on the basis of control data and a pre-stored program are disclosed. The control system controls the speed of a rotary motion motor that rotates the arm, the speed of the film transport motor and the distribution of those speeds, independently of each other. However, the apparatus is not adapted for use in an operating room on a patient in a prone position.